A. Iatrogenic Effects of Implantable Devices
Implantable medical devices made of various materials may cause a number of iatrogenic effects in patients. First, catheters, artificial heart valves, artificial joints, shunts, implanted leads for electrical stimulation devices, and vascular grafts can serve as foci for infection of the body. Infection is promoted by the tendency of bacterial organisms to adhere to the surfaces of implantable devices and, while adherent, to resist destruction by phagocytic cells that normally would destroy these organisms.
Second, catheters, vascular grafts and other implantable devices also tend to serve as a nidus, or focus, for the formation of thrombi (blood clots). This is because the surfaces of the implanted materials may activate non-cellular plasma clotting factors. Furthermore, platelets which adhere to the surfaces of these materials become activated and form thrombi. The procoagulant activities of many materials can prevent their use in vivo, or can greatly diminish their useful lifetime, as in the case of vascular access devices such as catheters. Finally, even materials which are chemically inert may act as foci for the formation of inflammatory lesions such as granulomas, resulting, in many cases, in the necessity for removal of the implanted device.
Therefore, there is a need for methods to render the surfaces of implantable materials less thrombogenic, less pro-inflammatory and less receptive to potentially infective bacteria.